Clang compiler defines fallthrough, but wrongly detects QT_HAS_CPP_ATTRIBUTE(fallthrough).
This makes compiler breaks compilation due clang be expecting
clang::fallthrough.
Change the order makes the exceptions. clang/gnu, been tested before
the generic, setting then proper defines at end.
LLVM-bug: https://bugs.llvm.org/show_bug.cgi?id=33518
Change-Id: Ic287e9028936af3bdade5c1ee319ca8914b36ea7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>